The present invention relates to the improvement in a method of corrosion, sound and vibration-proofing a metal structure wherein a coating of visco-elastic material is applied onto said metal structure and wherein selected portions or surfaces of said metal structure are protected from having the visco-elastic material applied thereto by placing masking members onto said surfaces or portions to be protected and the masking members then removed after the coating of said visco-elastic material has been applied to the metal structure. More particularly, the present invention relates to the improvement in a method of corrosion, sound and vibration-Drooling a metal structure, comprising employing as said masking members this thermoplastic foam-walled masking members.
Visco-elastic materials such as synthetic resin, rubber, asphalt are coated on the surface of a metal structure such as the underside of the floor of cars for the purpose of corrosion, sound, and vibration proofing. Said coating layer of visco-elastic materials covers the surface of said metal structure to protect said surface from flying stones; it seals the joined parts of the surface from water and corrosion. At the same time, said coating layer absorbs sound from the outside and vibration of the surface of said metal structure to exhibit a sound and vibration-proofing effect. Accordingly, said coating layer must be thick for a remarkable sound and vibration-proofing effect and usually the desirable thickness of said coating layer may be 500 to 2000 .mu.. Therefore, said thick coating layer obstructs the firm attachment of parts such as bolts, nuts, brackets, frames and the like to the surface of said metal structure.
Further, said metal structure usually has many holes for cables, operation wires and the like, and for drainage and the like. In cases where said metal structure has holes, said visco-elastic material must be prevented from going into said holes when said visco-elastic material is coated on the surface of said metal structure. Especially in cars, said visco-elastic material must be prevented from going into the holes that are in the outer panel which would give a bad appearance.
Therefore, it is necessary to protect such portions or surfaces of said metal structure by masking members and then coat the surface of said metal structure with said visco-elastic material. After coating, said masking members may be removed from said portions or surface of said metal structure.